generally
suggested by the term exposition.

Definition.

Definition of a word means giving its limits or boundaries. Of man it
might be said that it is a living animal, having a strong bony
skeleton; that this skeleton consists of a trunk from which extend
four limbs, called arms and legs, and is surmounted by a bony cavity,
called a skull; that the skeleton protects the vital organs, and is
itself covered by a muscular tissue which moves the bones and gives a
rounded beauty to their ugliness; that man has a highly developed
nervous system, the centre of which is the brain placed in the skull.
So a person might go on for pages, enumerating the attributes which,
taken together, make up the general idea of man.

Exposition and Description distinguished.

This sort of exposition is very near description; indeed, were the
purpose different, it would be description. The purpose, however, is
not to tell how an individual looks, but to place the object in a
class. It is therefore not description, but exposition. Moreover, the
method is different. In description those characteristics are given
that distinguish the object from the rest of the class; while in
exposition those qualities are selected which are common to all
objects of its class.

Logical Definition.

On account of the length of the definition by an enumeration of all
the attributes, it is not frequently used except in long treatises.
For it there has been substituted what is called a _logical
definition._ Instead of naming all the characteristics of an object, a
logical definition groups many attributes under one general term, and
then adds a quality which distinguishes the object from the others of
the general class. Man has been defined as the "reasoning animal." In
this definition a large number of attributes have been gathered
together in the general term "animal;" then man is separated from the
whole class "animal" by the word "reasoning." A logical definition
consists, then, of two parts: the general term naming the genus, and
the limiting term naming the distinguishing attribute called the
differentia.

Genus and Differentia.

Genus and differentia are found in every good definition. The _genus_
should be a term more general than the term defined. "Man is a person
who reasons" is a poor definition; because "person" is no more general
than "man." "A canine is a dog that is wild" is very bad, because
"dog," the general term in the definit